Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761832AbXFDT0g (ORCPT ); Mon, 4 Jun 2007 15:26:36 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759132AbXFDT00 (ORCPT ); Mon, 4 Jun 2007 15:26:26 -0400 Received: from www.osadl.org ([213.239.205.134]:55554 "EHLO mail.tglx.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1758829AbXFDT0Y (ORCPT ); Mon, 4 Jun 2007 15:26:24 -0400 Subject: Re: iperf: performance regression (was b44 driver problem?) From: Thomas Gleixner To: Stephen Hemminger Cc: Ulrich Drepper , Maximilian Engelhardt , Michael Buesch , linux-kernel , linux-wireless , Arnaldo Carvalho de Melo , Jeff Garzik , Gary Zambrano , netdev@vger.kernel.org, Andrew Morton , Ingo Molnar In-Reply-To: <1180983647.4404.38.camel@chaos> References: <20070525172431.60affaca@freepuppy> <200705281944.05030.maxi@daemonizer.de> <1180380230.3657.3.camel@chaos> <200706031826.06891.maxi@daemonizer.de> <1180939188.4404.5.camel@chaos> <20070604090918.42386fbb@freepuppy> <1180974958.4404.24.camel@chaos> <20070604095924.651d91c8@freepuppy> <1180978368.4404.29.camel@chaos> <20070604105158.31ede1f5@freepuppy> <1180983647.4404.38.camel@chaos> Content-Type: text/plain Date: Mon, 04 Jun 2007 21:26:18 +0200 Message-Id: <1180985178.4404.48.camel@chaos> Mime-Version: 1.0 X-Mailer: Evolution 2.10.1 (2.10.1-4.fc7) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1026 Lines: 28 On Mon, 2007-06-04 at 21:00 +0200, Thomas Gleixner wrote: > > > > Yes, the following patch makes iperf work better than ever. > > But are other broken applications going to have same problem. > > Sounds like the old "who runs first" fork() problems. > > Not really. The fork() "who runs first" problem is nowhere specified. > > usleep(0) is well defined: > > .... If the value of useconds is 0, then the call has no effect. > > So the call into the kernel has been wrong for quite a time. > Just for clarification: I'm not saying that we should break the (broken) user space ABI. I'm going to work out a patch which prints out a warning (limited number per boot) and emulating the old behavior by a call to yield() along with an entry into (mis)feature-removal.txt. tglx - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/